Improvement in processes of producing gelatine relief-plates for printing



UNITED STATES PATENT QFFICE.

WILLIAM MUMLER, OF BOSTON, MASSACHUSETTS.

IMPROVEMENT IN PROCESS ES 0F PRODUCING GELATINE RELIEF-PLATES FORPRINTING.

Specification forming part of Letters Patent No. [63,5 14, dated May 18,1875 application filed J une 2, 1874.

worked more or less successfully, all of which are founded upon thediscoveries of Mungo Ponton, an English chemist, in 1839, and M.Poitevin, a French engineer, in 1855, viz., that bichromatized gelatine,when acted upon by light, became insoluble in water, and also that itpossessed the properties of lithographic stone, and might be used assuch.

In order to more clearly set forth my invention, orits distinguishingfeatures, as compared with thevarious processes now in use, I will heregive a short summary of the main features of the more prominentprocesses now in use.

In photo-lithograph y and photo-zincograpliy a transfer is made on stoneor zinc, respectively, by means of gelatine, and the printing is donefrom the surface of the stone or zinc by means of lithographic ink andpress.

In photo-galvanography the gelatine film orplate, after having thepicture printed thereon, and the parts not acted upon by the lightswollen by water, is made to serve as the basis of electrotyping.

In the Woodburytype a sheet of gelatine from which the parts not actedupon by light have been washed away is used as the means of obtaining,by hydraulic pressure, a metal mold. This mold is filled, for everyimpression, with gelatine containing coloring matter, and the print isreally an embossing of colored gelatine 011 the sheet of paper.

In photo-collographic printing, or the heliotype process, the printingis directly from the flat level surface of the sheet of gelatine, in thesame manner that lithographs are printed from stone, the superfluouschemicals contained in those parts not previously acted upon by thelight having been washed out without washing away the gelatine.

My improved process differs from all these, and will be best understoodby adescription of the various operations in detail which go to make upthe complete process, which I will now proceed to give as follows:

In the preparation of the gelatine plate I use the followingingredients, in about the proportions named below: Gelatine, one ounce;fresh water, seven ounces; glycerine, two drams saturated solution ofbichromate of potash, two drams. These ingredicuts are placed in avessel and subjected to a gentle heat, and when thoroughly dissolved andmixed the mass is poured upon a smooth, level metal or glass plate,provided with ledges raised about one-fourth of an inch above its uppersurface around its outer edge, until the fluid mass is even with thetops of said ledges, the surface of said plate having been previouslyprepared by rubbing it with tallow to prevent the gelatine from adheringthereto. The plate, with the gelatine thereon, is then put away in adark room to dry. When thoroughly dry the gelatine film is removed fromthe glass or metal plate and placed under a photographic negative, andexposed to the light under the direct rays of the sun a suflicientlength of time to print thereon a picture from the negative in contacttherewith. It is then removed from under the negative, and secured to abase of glass, metal, or other suitable material, with the face orprinted side uppermost, by means of liquid glue, or any other suitableadhesive material that can be used in a cold state. The upper surface isthen made level and true by grinding the surface with emery paper orcloth, or other suitable abrading material, attached to a block of woodor other suitable material having a true and level surface.

To prevent the emery or other abrading material from scratching, I rubthe surface with tallow until all the interstices are filled. The plateof gelatine, with the picture printed thereon, is then treated withacetic acid by pouring it upon its upper surface, and brushing suchsurface with a soft bristle brush, to assist the acid in dissolving thegelatine not acted upon by the light. Those parts acted upon by thelight, being rendered insoluble thereby, are unaffected by the acid,and, as a consequence, are left standing out in relief by the gradualdissolving or eating away of those parts not acted upon by the light.Then a sufficient depth has been obtained, or when the acid hasdissolved or eaten away the gelatine as deep as the light haspenetrated, (which is indicated by a slight curving or croolzing of thestraight lines,l the acid must be immediately washed off with water atabout bloodheat. If any trace of acid should remain it may heneutralized by exposing the plate to the fumes of ammonia.

If sufficient depth has not been obtained by this one treatment theinterstices or parts eaten away by the acid may be filled or coated witha paste composed of mucilage or other suitable gum and bone-black; orsaid parts may be coated with india-ink, blackshellac-varnish, or anyopaque or semi-transparent substance which will prevent the passage ofthe actinic raysof light through the same, and that may be readilyremoved again without injury to the gelatine plate.

Up to this time all the operations upon the gelatine plate, except whileunder the negative, must be performed in a dark room, or in an antiactinic light. The plate covered or partially covered with thebone-black paste or other protective coating may now be exposed to theactinic light without the negative, the paste or other coatingpreventing the light from acting, except upon the lines left standing bythe acid, and which are not covered by the paste.

This exposure may continue for an indefinite time, or until the raisedlines become very hard and the light has penetrated and acted upon thegelatine to a sufficient depth. It is then taken into the dark roomagain, where the paste or other coating is removed by applying theretothe proper solvent for the coating usedas, for instance, if the paste ofmucilage and bone-black be used, cold water will dissolve it, and if avarnish be used to hold the coloring matter to render the coatingopaque, alcohol should be used as a solvent. \Vhen this has been donethe plate is again treated with acetic acid, as before. The plate maythen be dried in the light until it becomes hard in all its parts, atwhich time it is ready to electrotype in the same manner as a woodcut iselectrotyped.

It is well known that the face-surface of type, wood-cuts, and otherplates from which printing is to be done, must be true, straight, andlevel, in order that good work may be produced therefrom; but this hasnever been fully or satisfactorily accomplished in any of the processesof producing prints by means of gelatine plates, from the fact that inremoving the gelatine from .the original surface on which it was dried,and fastening the same to its base, it is very difficult to preserve thelevel surface, as well as the fact that the gelatine film, when dry, isnot sure to be of an even thickness, its upper surface sometimes beingquite irregular and uneven.

Another difficulty heretofore encountered by experimenters in trying toproduce gelatine reliefdates has been that the outer edges of the linesleft standing in relief after treating the plate with a solvent turn orcurve upward, and thereby destroying the even level surface thereof, theeffect of which is to make the lines, when printed, rough and imperfect.This difficulty is evidently occasioned by the partially insolublenature of the outer crust or coating of the gelatine film, which in allthe known processes is preserved intact. This outer crust, from somecause, is partially insoluble, and of a more contractile nature than therest of the plate.

To obviate these objections, to give to the gelatine plate a true,straight, and even surface, and prevent the turning up of the edges ofthe lines, I grind the face-surface of the gelatine plate after thepicture has been printed thereon, and after the gelatine film has beenpermanently secured to its base, as previously described.

Another great difficulty heretofore met with has been occasioned fromthe use of hot water as a solvent for the parts unaffected by the actionof light in printing the picture on the gelatine plate, which hasheretofore been the practice.

Gelatine has a great affinity for hot water and is easily dissolvedtherein, and in using it to cut away the parts of the plate not actedupon by the light the heat from the water penetrates the whole plate,and partially dissolves or softens the whole plate and throws the linesout of shape.

To obviate this difficulty I use acetic acid in a cold state as asolvent, which affects the gelatine plate only so far as it has not beenacted upon by actinic light, acetic acid having no effect uponbichromatized gelatine that has been exposed to the action of actiniclight when said acid is used in a cold state; but in the same cold statesaid acid is a very ready solvent of gelatine, however hard, if it hasnot been exposed to the action of actinic light, and, therefore, itfollows that the lines, however fine, are preserved intact and preventedfrom being thrown out of shape.

What I claim as new, and desire to secure by Letters Patent of theUnited States, is-

1. The process herein described of obtainin g level, straight, and truesurfaces on gelatinous films, from which to produce reliefplates forprinting from, by grinding the surface of said film with emery-cloth orother suitable abrading material properly extended upon and secured to atrue fiat surface of wood or other suitable material, substantially asdescribed.

2. The process of producing relief-surfaces upon gelatine plates byphotographing or printing from a photographic negative the picture to bereproduced upon the surface of said gelatine plate, grinding the surfaceof the plate either before or after printing thereon the picture, andthen treating it with acetic acid, substantially in the manner hereinset forth and described.

3. The process herein described of producing gelatine relief-plates byphotographing or printing from a photographic negative or positive uponthe surface of the gelatine plate the picture to be produced in, relief,treating the plate with acetic acid until it has eaten away the gelatineto as great a depth as possible without injury to the lines, removingthe acid and coating, or filling the parts acted upon by the acid with apaste made of boneblack and any suitable gum, or with indiaink, blackshellac-varnish, or other opaque or semi-transparent substance, thenexposing the plate to the direct rays of light without the negative orpositive plate, and, after removing the paste or other opaque orsemitransparent substance, treating the gelatine plate with acetic acida second time, substantially as described.

4. In the process of producing gelatine relief-plates, treating theplate, after a partial relief has been produced, to a coating ofboneblack paste, india-ink, black shellac-varnish, or other opaque orsemi-transparent substance, substantially in the manner hereindescribed, forzthe purpose specified.

5. The method of preventing the emery or other abrading material fromscratching the surface of the gelatine plate by filling the intersticesof the abrading-surface with tallow or equivalent material,substantially as described.

1 Executed at Boston this 29th day of May,

WILLIAM H. MUMLER.

Witnesses:

N. O. LOMBARD, WM. 1?. EDWARDS.

